CSC151.02 2003F, Class 11: Conditionals, Continued

Admin:
* Bad Michael!  Don't miss class and make your advisor cranky.
* Questions on the homework?
* Sorry, I forgot a reading.  We'll go over it today.
* Two new readings: Characters, Strings
* MathLAN tutoring, Sunday-Thursday, 9-10 p.m.
* Sam and Reese critique your sites

Overview:
* Review
* Basic comparisons
* Type Predicates
* Boolean functions
* The cond operations
* Lab: Conditionals

Review:
* The if expression in Scheme
	(if TEST TRUE-PART FALSE-PART)
  * If the TEST evaluates to anything but false, evaluates TRUE-PART
  * If the TEST evaluates to false, evaluates FALSE-PART

What kinds of tests can you have?
* Comparisons
	(< x y)
	(> x y)
	(<= x y)
	(= x y)
	...
* Type predicates
	(number? x)
	(list? x)
	(null? x)
	(zero? x)
	(real? x)
	...
* Combine predicates
	(if (or (< x y) (< y z)) ... ...)
 	(or EXP1 EXP2)
  * If EXP1 evaluates to false and EXP2 evaluates to false, the value is false
  * If either does not evaluate to false, the value is something that is not false
	(and EXP1 EXP2)
  * If EXP1 evaluates to false or EXP2 evaluates to false, the value is false
  * Otherwise, it's some non-false value
	(not EXP1)
  * If EXP1 evaluates to something that is not false, this evaluates to false
  * If EXP1 evaluates to false, this is true.

Start the lab!  Ask questions when things get confusing.  We'll probably
continue tomorrow.

We'll finish the lab tomorrow.